Researchers Find Way to Track and Trap Giant Hornets Using Sex Pheromones

The world’s largest hornet is known for its gruesome nickname—the murder hornet. The Asian giant hornet (Vespa mandarinia) earned the name because it crawls into honeybee hives and tears the heads off the bees.

Although researchers think the name might be overly dramatic, they agree the damage done by the invasive species is worrisome. In a new study, scientists have found a way to trap and destroy these destructive insects.

“These hornets prey on a wide variety of insects, and are particularly known for their ability to attack and kill honey bee colonies,” study author James Nieh, a professor and bee researcher at the University of California San Diego, tells Treehugger.

“Prior work has shown that up to a third of worker bees in a colony can die during a single attack of these hornets, and this is for a honey bee species, Apis cerana, that has co-evolved with these hornets and has good defenses against them. Unfortunately, the European or Western honey bee (Apis mellifera ligustica) that is found in North America has no effective defenses against this hornet and thus is even more vulnerable.”

An added problem is that the hornets will also attack and kill other bees, which could negatively affect bee biodiversity.

Native to Asia, the hornet was accidentally introduced to North America and first spotted in 2019. Attacks by groups of giant hornets can sometimes wipe out entire honeybee colonies.

Researchers were studying how to eliminate these devastating pests. One possible solution is to identify the insect’s sex pheromones and use them to bait and trap other hornets.

Working with colleagues in China, Nieh identified the three main components of the Asian giant hornet queen’s sex pheromone. They used chemical analysis techniques such as gas chromatography and mass spectrometry, as well as two years of behavioral analysis, as they measured the responses of male antennae to the female sex pheromones.

Based on previous research with a related hornet, Vespa velutina, they suspected that similar glands in the giant hornet could produce sex pheromones. They tried extracts from various sternal glands until they found the ones that attracted the males.

“We then presented major pheromone components, a synthetic blend, and natural sex pheromone in sticky traps to catch males. We found that our traps captured thousands of giant hornet males, no females, and no other species,” Nieh says.

“Sex pheromones are widely used to monitor the presence of pest insects and to interrupt their reproduction. We hope that traps baited with synthetic sex pheromone help determine where giant hornets are found and perhaps also interrupt their reproduction.”

If a trap is able to capture hornets, then their colonies can more easily be found and removed.

The results were published in the journal Current Biology.

Sex Pheromone Traps

Nieh points out how sex pheromone traps have been used to control pest insects including medflies (aka Mediterranean fruit flies), spongy moths (formerly known as gypsy moths), and vine mealybugs.

Add the giant hornets to the list.

“Researchers could begin by setting out these traps in areas known to have giant hornets recently. This would help them test the traps,” Nieh says. “If successful, then setting out traps at increasingly greater distances from the known hornet range could inform scientists of where they can begin to search, perhaps helping to reduce the range spread of these hornets.”

Although the hornets are large and frightening, Nieh wishes people would stop using the “murder” nickname.

“These hornets, like many other predators, kill for their food. However, it would be incorrect to call predators such as lions, tigers, or wolves ‘murderers.’ The hornets are not murderers. They do not kill randomly. They are simply hungry and trying to find food for their young,” he says.

“It is true that beekeepers find many adult bees dead and unconsumed at the nest entrance, but this is because the hornets are after the young bee larvae inside the nest. I am afraid that the term ‘murder hornet’ is rather sensational and therefore become more common.”